Re: Why Doesn't IE5 use the DTD to Validate?

Subject: Re: Why Doesn't IE5 use the DTD to Validate?
From: Chris Lilley <chris@xxxxxx>
Date: Fri, 02 Apr 1999 17:54:41 +0200

Didier PH Martin wrote:
> 
> Hi Chris,
> 
> <YourComment>
> I would love to hear how you think that contextual selectors and
> attribute selectors are expected to work without structural integrity.
> <YourComment>
> 
> <Reply>
> Hoops a word missing, this should be: structural integrity _validation_.

Ok. I was being loose in some other posts, too.

So, in summary, for DOM and CSS1 or CSS2 to work in an interoperable
fashion:

The parse tree, in terms of the root node, all subelement nodes, all
attributes on each element node, and whether any attributes are declared
to be ID and whether any attributes are declared to be NMTOKENS, must
all be present and correct. That will give *consistent* results in all
implementations.

Stylesheets may still give *incorrect* results, if the document is not
valid and if some selectors/patterns assume the correct content models.

> Structural integrity is the responsibility of the emitter. 

Yes, but

a) they will only take that responsibility if it buys them something
b) if it seems to usually work anyway without validating, they don't
think it buys them anything

> However, when
> electronic commerce transactions are the kind of operation done. Validation
> may be necessary for the receiver to be sure that the transaction is OK, so
> in that case a double check may be necessary A) at the emitter end and the
> receiver end. 

Electronic commerce is just one example where validation must be
insisted upon. It is not the only example, and some examples include
document display.

The thing to remember is, there is more being built using Web
specifications than just the typical, joe passive consumer taking a
break from watching the television sort of "browsing". There are other
sorts of browsing and there are other sorts of document transfer and
display and other usage scenarios.

If, in the documentation for the aircraft I am flying on or the nuclear
plant that generates my electricity or the maintenence manual for a
blood gas analyser whose results my doctor is depending on, the document
is invalid because

<!ATTLIST failure-condition severity
(silent-redundant|minor|fixat6months|fixin24hours|urgent|emergency|criticalhalt)
#REQUIRED>

and the required severity attribute is missing, and the style sheet has

diagnostic fault failure-condition[severity=criticalhalt]:before
  {content: "Shut this thing down NOW before she blows"'
   color: red; background: black;
   font-size: 8em; text-decoration: blink }

I certainly want to know about it and I want a validation check each
time the document is viewed.

> However, the interpreter in that case is probably not a
> browser but an other kind of application.

All browsers are equal, but some are more equal than others. And, some
things are more important than electronic commerce.

--
Chris


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